JPH0498268A - Image forming timing signal generator for color electronic photographing device - Google Patents

Abstract

PURPOSE:To correct variations in the fluctuations of a power source voltage and in the detecting positions of a light shielding plate 24 caused by a noise, etc., and to prevent the lag of timing when an image forming processing is carried out by providing an original position detecting means, a pulse signal output signal, and an image forming timing signal output means. CONSTITUTION:The original position of a rotary drum is detected by the original position detecting means (photointerrupter) 22, and an original position signal is outputted whenever the drum is rotated once, while a pulse signal output means (encoder) 18 outputs a pulse signal for generating a large number of pluses at one-rotation of a driving motor in synchronization with the rotation of the driving motor. Then, these signals are supplied to the image forming timing signal output means 26 and 28, on image forming timing signal is outputted whenever the pulse of the pulse signal obtains a previously set fixed number corresponding to one-rotation of the rotary drum, basing on the original position signal as a reference, and the image forming processing is carried out according to the outputted image forming timing signal. A timing signal is outputted based on the number of the pulses of the pulse signal generated in synchronization with the rotation of the driving motor 12 rotating/driving the rotary drum via a speed reducer 14, so that a difference is less, the lag of the image forming timing of plural colors is reduced, and the color slurring of a color image is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color electrophotographic apparatus, and more particularly, to a timing signal generating apparatus for repeating image forming processes of different colors in synchronization with the rotation of a rotating drum. be.

Conventional technology A rotating drum with a photoreceptor attached to its outer periphery is rotated at a constant speed, and charged and exposed in accordance with an image forming timing signal output every time the rotating drum rotates.

A color electrophotographic device that forms a color image on the photoreceptor by performing an image forming process such as development and repeating the image forming process multiple times for different colors is used in, for example, a color copying machine or a printer. There is. and,
Conventionally, the above-mentioned image forming timing signal is obtained by disposing a transmissive photo ink club in a fixed position member, and by providing a light shielding plate on the rotating drum to block the light from the photo ink club, one rotation of the rotating drum. The signal output from the photo ink club was used in each case.

Problems to be Solved by the Invention However, the repeat detection accuracy of such a photo ink printer is not necessarily sufficient, and the timing of image formation for multiple colors is shifted, for example, when scanning is performed using a laser, several scanning lines may be There is a problem in that a positional shift occurs by a certain amount, and a color shift occurs in a color image formed on a photoreceptor.

To explain specifically using FIG. 1, a transmissive photo ink converter 22 is arranged in a fixed position near the rotating drum 10, and is protected by a light shielding plate 24 provided on the outer peripheral side of the rotating drum 10. Since the optical path of the photo ink converter 22 is blocked, the original position signal SA, which generates a pulse every time the rotating drum IO rotates, is transmitted to the photo ink converter 2.
2, and the original position signal SA is used as a timing signal.
As shown in FIG. 3, the detection window 40 has a width W of about 0.5 mm in the rotation direction of the rotating drum 10.
Since light is projected and received through the light shielding plate 24, a detection error in the width dimension W occurs in the amount of movement of the light shielding plate 24, in other words, the amount of movement of the outer peripheral portion of the rotating drum 10. That is, when the optical path of the photo ink clubter 22 is blocked by the light shielding plate 24, the original position signal SA changes within the width dimension W as shown in FIG. As a result, the detection position of the light shielding plate 24 varies within the width W thereof.

The present invention has been made against the background of the above-mentioned circumstances, and its purpose is to prevent timing shifts when performing image forming processing for a plurality of colors.

Means for Solving the Problems In order to achieve the above object, the present invention rotates a rotating drum having a photoreceptor on its outer periphery at a constant speed via a reduction gear by a drive motor, and the rotating drum l, A color image is formed on the photoreceptor by performing image forming processing such as charging, exposure, and development according to an image forming timing signal outputted every rotation, and by repeating the image forming process multiple times for different colors. In color electrophotographic equipment,
(a) an original position detecting means for detecting the original position of the rotating drum and outputting an original position signal for each rotation of the rotating drum; a pulse signal output means for outputting a pulse signal that synchronously generates a large number of pulses in one rotation of the drive motor;
C) the in-situ signal and the pulse signal are provided;
and an image forming timing signal output means for outputting an image forming timing signal every time the pulse signal reaches a predetermined constant number corresponding to one revolution of the rotating drum, with the original position signal as a reference. Features.

Operation and Effects of the Invention In such an image forming timing signal generation device for a color electrophotographic apparatus, the original position of the rotating drum is detected by the original position detecting means, and an original position signal is output every time the rotating drum rotates. On the other hand, the pulse signal output means outputs a pulse signal that generates a large number of pulses in one rotation of the drive motor in synchronization with the rotation of the drive motor. and,
The original position signal and pulse signal outputted from the original position detection means and the pulse signal output means, respectively, are supplied to the image forming timing signal output means, and the pulses of the pulse signal are outputted once per rotation of the rotating drum based on the original position signal. An image forming timing signal is output every 2, which is a predetermined constant number corresponding to , and image forming processing is performed in accordance with the image forming timing signal.

Here, the image forming timing signal is output based on the number of pulses of a pulse signal generated in synchronization with the rotation of the drive motor that rotationally drives the rotary drum via a reduction gear, so Compared to the case where the configured device signal is used as an image forming timing signal as it is, there are fewer errors, and deviations in image forming timing of a plurality of colors with respect to rotation of the rotary drum are reduced, thereby preventing color shift in color images.

That is, the pulse signal output means generates a large number of pulses in synchronization with the rotation of the drive motor, and is composed of, for example, an encoder equipped with a photo ink club or the like, and is configured to generate a large number of pulses in synchronization with the rotation of the drive motor. Pulses with similar detection errors are generated, but since the rotation of the rotating drum is reduced by a predetermined reduction ratio than the rotation of the drive motor by the reducer, the detection error for the rotation of the rotating drum corresponds to that reduction ratio. Therefore, the detection error is smaller than the detection error for the rotation of the drive motor.

In addition, the synchronization error with respect to the original position signal is determined by the number of pulses of the pulse signal per rotation of the rotating drum, and if this number of pulses is small, the synchronization error of the imaging timing signal with respect to the original position of the rotating drum becomes large, so the drive motor The number of pulses of the pulse signal output from the pulse signal output means per rotation is, for example, several tens of μ in the amount of movement of the outer circumference of the rotating drum, that is, the amount of positional deviation of the photoreceptor.
It is set in consideration of the reduction ratio of the reducer, the diameter of the rotating drum, etc. so that a pulse is generated every m.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIG. 1, reference numeral 10 denotes a rotating drum of a color electrophotographic apparatus, which is rotationally driven by a drive motor 12 via a reducer 14, and has photosensitive paper 16 as a photoreceptor wrapped around its outer peripheral surface. ing. An encoder 18 is attached to the drive motor 12, and a pulse signal SP that generates a large number of pulses in synchronization with the rotation of the drive motor 12 is output to the motor drive circuit 20, while a drive signal SP is output from the motor drive circuit 20. SD is output to the drive motor 12, and the drive motor 12 is feedback-controlled so that the rotating drum 10 rotates at a predetermined constant speed. The encoder 18 corresponds to a pulse signal output means, and is a pulse signal S per rotation of the drive motor 12.
The number of pulses n of P is set to about 100, for example.

Further, the reduction ratio r of the reduction gear 14 is set to about ]/100, for example.

A transmissive photo ink converter 22 is fixedly disposed near the rotating drum 10, and the optical path of the photo ink converter 22 is blocked by a light blocking plate 24 provided on the side surface of the outer circumference of the rotating drum 10. By this, rotating drum I
A home position signal SA that generates a pulse is output every time the rotational position of O reaches the home position. This photo ink printer 2
2 corresponds to original position detection means.

Also, around the rotating drum 10, there is a paper feeding device that feeds the photosensitive paper 16 in synchronization with the original position signal SA, and a charger that charges the photosensitive paper 16. An exposure device that forms an image, a developing device that attaches toner to the electrostatic latent image and makes it visible, etc. are installed, and the above-mentioned charging, R light, development, etc. are performed every rotation of the rotating drum 1o. A color image is formed by performing image processing and repeating the image forming process multiple times for different colors.

Such a color electrophotographic apparatus is equipped with a control circuit shown in FIG. 2, and the pulse signal sp and original position signal SA are supplied to a frequency divider 26. Frequency divider 26
Also, an image forming signal SS is supplied from the microcomputer 30 for image forming timing control, and after the image forming signal SS is supplied, the pulse of the original position signal SA that is first supplied is Start frequency division of the pulse signal SP as a reference, and set the number of pulses of the pulse signal SP to 1.
/n2, and outputs a frequency-divided signal SB that generates a pulse every time the number of pulses reaches n2. The number of pulses n2 is predetermined as the number of pulses of the pulse signal SP per revolution of the rotary drum 10, that is, n/r. For example, when the number of pulses is n-100, the reduction ratio r = I / I 00
In this case, the number of pulses n2 is set to 10,000.

Therefore, this frequency-divided signal SB generates a pulse every rotation of the rotary drum 10, and is substantially the same as the original position signal SA. There is a detection error within the width dimension W of the detection window 40 shown in FIG.
This means the outer peripheral portion of 0, that is, the positional shift of the photosensitive paper 16. On the other hand, the encoder 18 that outputs the pulse signal SP is also configured with a photo ink converter, and generates a pulse having a detection error of the width dimension W with respect to the rotation of the drive motor 12. tram 1
0 is reduced by the reduction ratio rT by the reduction gear 14, so the detection error for the rotation of the rotary drum 10 is smaller than the detection error for the rotation of the drive motor 12, corresponding to the reduction ratio r. That is, assuming that the diameter of the encoder 18 is d12 and the diameter of the rotating drum 10 is d2, the detection error of the rotation of the rotating drum 10 by the encoder 18 is the amount of movement of the outer circumference of the rotating drum 10, that is, the amount of movement of the photosensitive paper 1.
At the positional deviation amount of 6, it becomes wrd2/d+, and w=
0.5. mm, r=1/100. dz /d+ =
In the case of 4, it is 20 μm. In other words, the original position signal SA has a maximum positional deviation of the photosensitive paper 16 of 0.5 mm, whereas the frequency-divided signal SB has a maximum positional deviation of only 20 μm, and one revolution of the rotating drum 10 It is detected with high precision.

The frequency-divided signal SB is then supplied to the selection circuit 28 together with the original position signal SA. The selection circuit 28 outputs the first image forming timing signal ST to the microcomputer 30 in synchronization with the pulse of the original position signal SA supplied first after the image forming signal SS is supplied, and thereafter, An image forming timing signal ST is synchronized with the pulse of the frequency divided signal SB.
is output to the microcomputer 30. That is, 2
Regarding the image forming timing signal ST after the th image forming timing signal ST, the image forming timing signal ST is outputted in synchronization with the frequency divided signal SB that is supplied every time the number of pulses of the pulse signal SP reaches a predetermined constant number n2. , this selection circuit 28 and the frequency divider 26 constitute image forming timing signal output means.

The microcomputer 30 outputs the image forming signal SS when a start button or the like is operated, and also controls the exposure device, the developing device, etc. by being supplied with the image forming timing signal ST from the selection circuit 28. The operation is controlled to perform image forming processing on the photosensitive paper 16. This image forming process is performed for a different color every time the image forming timing signal ST is supplied, that is, every rotation of the rotary drum 10, and the image forming process for a plurality of predetermined colors is performed on one sheet. By overlapping the photosensitive paper 16, a color image is formed on the photosensitive paper 16.

In this case, since the first image forming timing signal ST is output in synchronization with the pulse of the original position signal SA, the first image forming timing signal ST is
Although the image forming position of the second color is misaligned with respect to the photosensitive paper 16 within the range of the width dimension W, the image quality of the color image is not affected.

Since the second image forming timing signal ST is output in synchronization with the pulse of the frequency divided signal SB, the image forming position of the first color and the image forming position of the second color are different from each other. In between,
A positional shift occurs due to a detection error of the encoder 18 and a synchronization error with the first imaging timing signal ST, but the detection error of the encoder 18 is 20μ as described above.
m or less. Furthermore, the synchronization error is determined by the number n2 of pulses of the pulse signal SP per revolution of the rotary drum 10, and the number n2 of pulses is 1000 in this embodiment.
0, the outer circumference of the rotating drum IO is, for example, 500 m.
m, the synchronization error with respect to the first image forming timing signal ST is 500 mm/100 in the amount of movement of the outer peripheral portion of the rotating drum 10, that is, the amount of positional deviation of the photosensitive paper 16.
00=50 μm. Therefore, the positional deviation between the image forming position of the first color and the image forming position of the second color is 70 μm at the maximum.

Further, the third and subsequent image forming timing signals ST are the second and subsequent image forming timing signals ST.
Like the second image forming timing signal ST, it is output in synchronization with the pulse of the divided signal SB, so the image forming position of the second color and the image forming position of the third and subsequent colors are different from each other. In between, there is a detection error of the encoder 18, that is, a maximum of 2
Only a positional deviation of 0 μm occurs.

As described above, according to the color electrophotographic apparatus of this embodiment,
The positional deviation of the image forming position of multiple colors is up to 70 μm,
This is significantly smaller than the conventional positional deviation of 0.5 mm, and as a result, a high-quality color image with less color shift can be formed.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the embodiment described above, the first image forming timing signal ST is output in synchronization with the pulse of the original position signal SA, but the first image forming timing signal ST is The first imaging timing signal ST is output in synchronization with the first pulse of the pulse signal SP after the pulse of the signal SA, and the pulse signal SP is output based on the first imaging timing signal ST. It is also possible to divide the frequency and output the second and subsequent image forming timing signals ST. In that case, all image forming timing signals ST will be output based on the pulses of the pulse signal SP, eliminating synchronization errors and further reducing positional deviations in the image forming positions of multiple colors. drum 1
There is no problem even if the number of pulses of the pulse signal SP per rotation of 0 is relatively small.

Further, in the above embodiment, the image forming timing signal output means was constituted by the frequency divider 26 and the selection circuit 28, but the original position signal SA and the pulse signal SP are taken into the microcomputer 30, and the image forming timing signal is outputted by software. ST may also be generated.

Further, the color image to be formed does not necessarily have to be full color, and the present invention can be similarly applied to a color electrophotographic apparatus that prints two or more colors in a superimposed manner.

Although other examples are not provided, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a drum rotation drive section of a color electrophotographic apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a circuit for extracting an image forming timing signal in the apparatus of FIG. 1. FIG. 3 is a perspective view of the photo ink club in the apparatus of FIG. 1. FIG. 4 is a diagram showing the output signal of the photo ink clubter. 10: Rotating drum 12: Drive motor 14: Reducer 16: Photosensitive paper (photoreceptor) 18: Encoder (
Pulse signal output means) 22: Photo ink club (original position detection means) SA: Original position signal SP; Pulse signal ST: Image forming timing signal

Claims (1)

[Scope of Claims] A rotating drum having a photoreceptor on its outer periphery is rotated by a drive motor at a constant speed via a speed reducer, and is charged and charged in accordance with an image forming timing signal outputted every time the rotating drum rotates. In a color electrophotographic apparatus that forms a color image on the photoreceptor by performing image forming processing such as exposure and development and repeating the image forming process multiple times for different colors, the original position of the rotating drum is detected. a home position detection means that outputs a home position signal every time the rotating drum rotates; a pulse signal output means for outputting a pulse signal that outputs a pulse signal; the home position signal and the pulse signal are supplied, and the pulse of the pulse signal is a predetermined pulse that corresponds to one revolution of the rotating drum, with the home position signal as a reference. An image forming timing signal generating device for a color electrophotographic apparatus, comprising: an image forming timing signal output means for outputting an image forming timing signal every time a certain number is reached.